Gates which are vertically reciprocable between open and closed positions are used in various systems such, for examples, as, when flow volumes through sluices, weirs and aqueducts are large typically for the control of water which may be and often is waste waters or other liquids.
The requirements of such gates illustrate the problems with which the present invention is concerned. Movement of such a gate between its open and closed positions is attended by frictional resistance which factor and the size of the gate determine the type of mechanism to be used to reciprocate it. The prime requirement of any such gate is that it be operable to seal effectively the port it controls and attendant friction adversely affects seal life.